A percussion primer is a primary explosive composition that is commonly used to ignite a secondary explosive composition or charge. The primary explosive composition is more sensitive to impact than the secondary explosive composition and burns or deflagrates for a short period of time before detonating. To be effective as a percussion primer, the primary explosive composition must have a relatively low activation energy for a given output energy. In contrast, conventional explosives and insensitive explosives with similar output energies have higher activation energies. Since the primary explosive composition is more sensitive to impact, the primary explosive composition ignites and detonates before the secondary explosive composition. In contrast, the secondary explosive composition is relatively stable and does not detonate until initiated by the primary explosive composition.
Many ingredients of conventional percussion primers are toxic and their use is restricted by the Environmental Protection Agency. These ingredients include styphnate and picrate salts, heavy metal compounds, or diazodinitrophenol (“DDNP” or dinol). The heavy metal compounds include compounds of mercury, lead, barium, antimony, beryllium, cesium, cadmium, arsenic, chromium, selenium, strontium, tin, or thallium, such as lead styphnate or barium styphnate, or mercury fulminate. Upon ignition, a percussion primer that includes one of these ingredients emits toxic lead oxides or toxic compounds of other heavy metals, such as oxides of cesium, barium, antimony, or strontium. DDNP is also toxic because it is known to cause allergic reactions and is possibly carcinogenic.
Conventional percussion primers also commonly include oxidizers, such as potassium nitrate, potassium perchlorate, or potassium chlorate, which are also toxic. Potassium nitrate and potassium chlorate are also hygroscopic, which increases the complexity of processing the percussion primer because the potassium nitrate and potassium chlorate must be stored in ovens and cannot be used on wet days. In addition to requiring specialized storage, hygroscopic materials cause the percussion primer to have a sticky consistency, which affects loading and processing of the percussion primer. Other hygroscopic ingredients, such as gums, are also used in conventional percussion primers. Gums typically gain about 30% of the gum weight in moisture when exposed to humid conditions. In addition to being hygroscopic, gums are obtained from natural sources and, therefore, exhibit characteristics which may vary from batch to batch. Some ingredients of conventional percussion primers are also corrosive, such as potassium chlorate, which is corrosive to steel and corrodes a gun barrel when the percussion primer is used in small arms ammunition.
To reduce health and environmental risks, percussion primers that are free of lead have been developed. U.S. Pat. No. 4,522,665 to Yates, Jr. et al. discloses a percussion primer that includes titanium and potassium perchlorate. U.S. Pat. No. 5,417,160 to Mei et al. discloses a percussion primer that contains calcium silicide, DDNP, and an alkaline or alkaline earth nitrate. U.S. Pat. No. 5,167,736 to Mei et al. discloses a percussion primer that includes DDNP and boron and U.S. Pat. No. 5,567,252 to Mei et al. discloses a percussion primer that includes DDNP, boron, and iron oxide. U.S. Pat. Nos. 4,963,201 and 5,216,199 to Bjerke et al. disclose a percussion primer that includes DDNP, strontium nitrate, tetracene, and a nitrate ester fuel. U.S. Pat. No. 6,478,903 to John, Jr. et al. discloses a percussion primer that includes bismuth sulfide and potassium nitrate or zinc sulfide and aluminum nitrate. U.S. Pat. No. 4,581,082 to Hagel et al. discloses a primer charge that includes zinc peroxide, DDNP, and/or a strontium salt of mono- and/or dinitrodihydroxydiazobenzene.
International Application WO 01/21558 to Nesveda et al. discloses an ignition mixture that includes a high explosive and a sensibilizer, such as tetracene, tetrazole, a tetrazole derivative, or a tetrazole salt. The high explosive is a nitroester, such as penthrite, nitrocellulose, or hexanitromanite, or a nitramine, such as hexogen (“RDX”), octogen (“HMX”), or tetryl. The ignition mixture also includes powdered boron as a fuel and an oxidizing agent, such as an oxide of copper, bismuth, zinc, iron, manganese, vanadium, tin, molybdenum, or calcium.
In light of the problems mentioned above with conventional percussion primers, it would be desirable to produce a percussion primer that utilizes nontoxic, noncorrosive, and nonhygroscopic ingredients.